Quote:
Originally Posted by oil pan 4
Increasing compression is proven to increase efficiency in piston engines. The only reason you lower compression in a diesel is to reduce NOx, allow for more boost to be ran to boost power and reduce fuel economy.
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Nope, they did it so the motor wouldn't burn valves and fall apart, they could care less about NOx back when they made the change.
Quote:
Originally Posted by oil pan 4
Why do all these people want to reduce compression in hopes of increaseing fuel economy?
You think it would take less force to get the piston to TDC on the compression stroke and I can see that but that doesn't mean it will make the engine more efficient.
Notice all the OEMs have gone up in compression since the 1980s not down (except diesels, they all went down for emmissions reasons).
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The reason is typically reliability but also the fact that your engine is not going to automatically increase in efficiency as compression ratio goes up, in fact it can go down because of the massive dynamic frictional losses, egr and blowby
6.2 based engines like their 21:1 ratio but do not like high boost 5psi is actually the best without the fuel pressure turned up. (for economy.)